Aircraft often are required to be moved in and out of hangars and repositioned on airport aprons. Typically these aircraft are towed using a tug and tow bar, or a “towbarless” tug equipped with a winch and cradle for capturing and towing via nose landing gear. Fixed landing gear aircraft equipped with castering nose landing gear and sloped strut with or without aerodynamic wheel fairing have posed a unique towing challenge for tug operators.
Conventional tugs, equipped with a pintle hook, a towbar and aircraft specific towing head that plugs into the nose landing gear towing lugs, tend to break turning linkages and towbars are known to scratch wheel fairings as the towbar is being installed or removed. Additionally, pushing back an aircraft, with a short wheel base, castering nose landing gear, requires tedious reverse inputs by a skilled operator, who would often take several attempts to effectively position these aircraft.
“Towbarless” tugs are typically equipped with a cradle to raise the nose landing gear, a winch with strut strap to capture the aircraft onto the cradle and a holdback bar to prevent the nose wheel fairing from contacting the rear gate of the cradle. The holdback bar is known to damage sloped strut, oleo, or strut fairings as the bar needs to keep positive contact with the fairing that's not designed to be load bearing. Oleo fairings get damaged by the hold back bar when the tug operator hits a bump. As the oleo depresses, the fairing impacts the holdback bar. The problem is more likely if the oleo is under inflated. Additionally, wheel guidance tools placed on the cradle are known to damage the lower part of the wheel fairing.
“Towbarless” tug operators have used a combination of the conventional and “towbarless” methods by using an adapter that inputs into towing lugs and is winched via chain onto the cradle and positively secured by a front pintle hook. This method avoids the tedious reverse inputs of a conventional tug and tow bar, but nonetheless requires the time consuming task of securing the pintle hook in place on an adapter post and raising/lowering of the pintle jaw to positively secure the adapter in place. Another problem with the pintle hook and adapter method is the overall length of the pintle hook from the back of the cradle means certain models of aircraft have tires near the edge of the cradle. More importantly, some aircraft manufacturers tire/wheel fairing/towing lug configurations cannot be accommodated as a result. Plus the female steel adapter towing insert still tends to scratch nose wheel fairings.
The ‘pintle-hook towbarless adapter’ and ‘holdback bar’ methods open the nose landing gear capture process to operators using a dangerous practice called ‘scooping’. This involves driving the cradle under the nose wheel of an aircraft with ‘chocked’ main landing gear. The operation saves the time required to winch the aircraft on to the cradle, but there is a great risk of impacting the aircraft wheel fairing with the tug cradle.
Additionally there are various powered tow bars and combinations that use the conventional towing lugs and hold down or hold back mechanisms to tow these aircraft. Examples of these are a wheel guide and hook/loop fastener strap to hold the nose wheel down and prevent it from “jumping” out of the wheel guide. Or a tow bar type mechanism to winch the aircraft onto the cradle with wheel guide. These methods are time consuming to use and costly, since the solutions are generally aircraft specific, with some perhaps working on two aircraft types.